<template>
  <div
    class="al-color-svpanel"
    :style="{
      backgroundColor: background
    }"
  >
    <div class="al-color-svpanel__white"></div>
    <div class="al-color-svpanel__black"></div>
    <div
      class="al-color-svpanel__cursor"
      :style="{
        top: cursorTop + 'px',
        left: cursorLeft + 'px'
      }"
    >
      <div></div>
    </div>
  </div>
</template>

<script>
import draggable from '../draggable';

export default {
  name: 'al-sl-panel',

  props: {
    color: {
      required: true
    }
  },

  computed: {
    colorValue() {
      const hue = this.color.get('hue');
      const value = this.color.get('value');
      return { hue, value };
    }
  },

  watch: {
    colorValue() {
      this.update();
    }
  },

  methods: {
    update() {
      const saturation = this.color.get('saturation');
      const value = this.color.get('value');

      const el = this.$el;
      let { clientWidth: width, clientHeight: height } = el;

      this.cursorLeft = (saturation * width) / 100;
      this.cursorTop = ((100 - value) * height) / 100;

      this.background = 'hsl(' + this.color.get('hue') + ', 100%, 50%)';
    },

    handleDrag(event) {
      const el = this.$el;
      const rect = el.getBoundingClientRect();

      let left = event.clientX - rect.left;
      let top = event.clientY - rect.top;
      left = Math.max(0, left);
      left = Math.min(left, rect.width);

      top = Math.max(0, top);
      top = Math.min(top, rect.height);

      this.cursorLeft = left;
      this.cursorTop = top;
      this.color.set({
        saturation: (left / rect.width) * 100,
        value: 100 - (top / rect.height) * 100
      });
    }
  },

  mounted() {
    draggable(this.$el, {
      drag: (event) => {
        this.handleDrag(event);
      },
      end: (event) => {
        this.handleDrag(event);
      }
    });

    this.update();
  },

  data() {
    return {
      cursorTop: 0,
      cursorLeft: 0,
      background: 'hsl(0, 100%, 50%)'
    };
  }
};
</script>
